The spinal column is critical in human physiology for mobility, support, and balance. The spine column protects the nerves of the spinal cord, which convey commands from the brain to the rest of the body, and convey sensory information from the nerves below the neck to the brain. The spinal column is made of two basic components—vertebrae (bone) and intervertebral discs (gel-like cushions that absorb pressure and prevent vertebrae from rubbing together). A number of vertebrae and intervertebral discs stack together to form a column that provides support and structure for the body while still allowing a large degree of motion and flexibility and protecting the spinal cord. Even minor spinal injuries can be debilitating to the patient, and major spinal injuries can be catastrophic. The loss of the ability to bear weight or permit flexibility can immobilize the patient. Even in less severe cases, small irregularities in the spine can put pressure on the nerves connected to the spinal cord, causing devastating pain and loss of coordination. Examples of causes of such pain include changes in disc height and improper motion of vertebrae.
Surgical procedures on the spine often include the immobilization of two or more vertebrae, typically by fusing vertebrae together. As a result of such surgical invention, disc height may be corrected, and vertebrae may be immobilized, while fusion occurs.
One of the more common methods for achieving the desired immobilization is through the application of bone anchors (most often introduced into the pedicles associated with the respective vertebrae to be fixed) that are then connected by rigid rods locked to each pedicle screw. A significant challenge with such bone anchors is securing the pedicle screws without breaching, cracking, or otherwise compromising the pedicle wall, which may occur if the screw is not properly aligned with the pedicle axis. Moreover, such pedicle screw systems require invasive surgery. Therefore, a need continues to exist for systems for fusing vertebrae that can be used as alternatives to pedicle screws and can be used in minimally invasive surgical procedures.